Supplementation with quercetin, a plant pigment found in capers, cilantro, fennel, onions, red leaf lettuce, watercress, elderberries, asparagus, kale, cocoa, apples and chia seeds, can significantly reduce both diastolic and systolic blood pressure, lowering each by about three milliliters/Hg, reports a new review of research published in the Oxford Academic Journal, of 17 clinical studies that tested 896 participants. Quercetin also improved HDL cholesterol and triglyceride levels when consumed for eight weeks or more.